The present invention generally relates to airborne ancillary turbomachinery, and in particular to a method and device for mounting such equipment to flight vehicle structures.
A typical flight vehicle, such as an aircraft, may include a turbomachine such as an Auxiliary Power Unit (APU) 10, partially shown in FIG. 1, used to provide electrical and pneumatic power to various parts of the aircraft (not shown) for environmental control, interior lighting, electronic power, and starting a main engine.
The conventional APU 10 may be mounted to the aircraft by means of struts or links attached to an APU gearbox pad 19. As shown in FIG. 2, a standard cloverleaf strut mounting assembly 11 (here shown in an exploded view) may include a finger mount 13, a stud adapter 23, a first vibration isolator 27, and a second vibration isolator 29. The stud adapter 23 may be removably attached to the conventional APU 10, typically by using mechanical fasteners. The finger mount 13 may be configured for removable attachment to proximate ends of a strut 15 and a strut 17. The distal ends of the struts 15 and 17 may be secured to the aircraft so as to provide support to the conventional APU 10.
A cloverleaf 21 may be configured to bear against the APU gearbox pad 19 and to mate with the stud adapter 23. The finger mount 13 may be mechanically secured to a stud 25 on the stud adapter 23 with a first vibration isolator 27 provided between the finger mount 13 and the stud adapter 23, and a second vibration isolator 29 and a washer 31 under a nut 33 threaded onto the stud 25.
Because there are a large number of flight vehicles currently in worldwide service which make use of the above standard cloverleaf strut mounting assembly 11 to install ancillary equipment, there exists a large, worldwide manufacturing base producing the standard mounting components. The relatively low cost and ready availability of these mounting components makes it desirable, when designing new ancillary aircraft equipment, to provide mounting pads compatible with the cloverleaf configuration. Accordingly, the present manufacturing base continues to produce the standard mounting components for new equipment as well as for the conventional equipment still in service.
Certain new ancillary equipment in the present state of the art is designed to be lighter and less costly, having fewer conventional hard pickup points for structural support and mounting. For example, a new auxiliary power unit may be designed without a gearbox to save weight and, consequently, would not have available a mounting surface, such as the APU gearbox pad 19, for attaching the standard mounting hardware. Such new equipment cannot utilize the standard mounting hardware and associated components described above, even though it remains economically feasible to continue using these components, even for new designs, and specialized mounting methods are used.
For example, an alternative mounting system is described in U.S. Pat. No. 5,183,223 issued to Cornax which discloses a first radial ring attached to an engine cowl and a second radial ring attached to an engine by a plurality of bolts. Outwardly extending tabs in the second ring mesh with grooves in the first ring to allow relative movement of the rings and thus provide for radial expansion as the engine heats up during operation. The mounting system disclosed by Cornax '223 is thus not compatible with standard mounting components. U.S. Pat. No. 6,401,448 issued to Manteiga et al. discloses a system for mounting an aircraft engine which includes mounting features disposed on the engine, such as on the combustor casing. The mounting features may be attached to a mounting frame that is bolted to a pylon. However, the mounting system disclosed by Manteiga et al. '448 also includes specialized supporting struts and mounting features for securing the radial rings to the aircraft structure and does not utilize standard mounting components.
There continues to be a need for a mounting apparatus for mounting ancillary equipment to a vehicle, wherein the mounting apparatus is capable of using standard struts, cloverleaf mounting components, and finger attachments.